Improvements in telecommunications systems have resulted in the ability to transmit voice and/or data signals along transmission lines at increasingly higher frequencies. Several industry standards that specify multiple performance levels of twisted-pair cabling components have been established. The primary references, considered by many to be the international benchmarks for commercially based telecommunications components and installations, are standards ANSI/TIA/EIA-568-A (/568) Commercial Building Telecommunications Cabling Standard and 150/IEC 11801 (/11801), generic cabling for customer premises. For example, Category 3, 4 and 5 cable and connecting hardware are specified in both /568 and /11801, as well as other national and regional specifications. In these specifications, transmission requirements for Category 3 components are specified up to 16 MHZ. Transmission requirements for Category 4 components are specified up to 20 MHZ. Transmission requirements for Category 5 components are specified up to 100 MHZ. New standards are being developed continuously and currently it is expected that future standards will require transmission requirements of at least 600 MHZ.
The above referenced transmission requirements also specify limits on near-end crosstalk (NEXT). Often, telecommunications connectors are organized in sets of pairs, typically made up of a tip and ring connector. As telecommunications connectors are reduced in size, adjacent pairs are placed closer to each other creating crosstalk between adjacent pairs. To comply with the near-end crosstalk requirements, a variety of techniques are used in the art.
Existing telecommunications products include plugs, outlets and connecting blocks. Each of these devices can suffer from crosstalk as the rate of transmission increases. To reduce this crosstalk, modular plugs have been developed utilizing several different approaches. Prior art plugs, such as those sold by Hubbell, AT&T, and Thomas & Betts use square wire contacts to reduce contact overlap. Other prior art plugs, such as those sold by Amp and RJ Enterprises use an inline load bar. Other prior art plugs, such as those sold by Stewart and Sentinel use a loadbar with a staggered, non-coplanar scheme.
Outlets have also been designed to reduce crosstalk as the rate of transmission increases. To reduce this crosstalk modular outlets have been developed utilizing resilient conductive pins with two resilient conductive pins entering the plug mating area from the rear as opposed to the usual front. Prior art devices such as that sold by Stewart have conductive pins 3 and 6 entering the plug mating area from the rear.
Connecting blocks have also been designed to reduce crosstalk. Current 110 type connecting systems are designed to support digital data transmission as well as analog/digital voice over unshielded twisted pair (UTP) media through the use of wiring blocks, connecting blocks and patch cords or jumpers. This system facilitates moves and rearrangements of circuits connected to end-users or equipment. These 110 type blocks use punch down insulation displacement contacts (IDC) to maximize density and ease of use. A limitation of prior art devices is the difficulty encountered when lacing and punching down twisted pair wiring. The tips of the 110 type blocks between the IDC pairs are typically blunt and require untwisting of the wire prior to lacing into the block. This could lead to excessive untwist in the pair and a loss of electrical performance. To reduce this crosstalk, conventional connecting blocks have been developed utilizing conductive shields (plates) between adjacent pairs such as those disclosed in U.S. Pat. Nos. 5,160,273 and 5,328,380.
While there exist plugs, outlets and connecting blocks designed to reduce crosstalk and enhance performance, it is understood in the art that improved plugs, outlets and connecting blocks are needed to meet increasing transmission rates.